Molecular characterization and an infectious clone construction of sweet potato leaf curl virus (SPLCV) isolated from Korea

Sweet potato leaf curl disease (SPLC D) was primarily identified in sweet potato fields in Korea in 2003, and the complete genomic sequence of sweet potato leaf curl virus (SPLCV) has been cloned. The genome of the Korean SPLCV isolate (SPLCV -KR) comprises 2,828 nucleotides with six open reading frames in DNA-A, similar to a monopartite begomovirus. Additionally, neither the genome B genomic component nor the DNA beta sequence was detected. The results of phylogenetic analysis using the maximum parsimony method showed that SPLCV -KR is more closely related to SPLCV -US (US) than SPLCV -CN (China) and SPLCV -JP (Japan). A tandem repeat dimer of SPLCV -KR was cloned and found to be infectious in sweet potatoes (Ipomoea batatas) via biolistic inoculation. The SPLCV -infected sweet potatoes exhibited mild leaf curl symptoms of SPLC D, and the newly-replicated viral DNA was detected via Southern blot analysis. Results of biotic, molecular, and phylogenetic characterization suggest that SPLCV -KR is a new strain of SPLCV and is importantly placed in the evolutionary progression from curtoviruses to begomoviruses.